Washington – Scientists heaped more criticism Thursday on the Obama administration’s claim that most of the Gulf of Mexico oil spill is gone, saying that it was too early to determine the remaining oil’s impact on the waters or marine life.

Most of the 4.1 million barrels of spilled oil remains in the environment even if it’s not visible, posing unknown consequences for sea life and the thousands of Gulf residents whose livelihoods depend on fishing, scientists said. They accused the Obama administration of painting a rosy picture while revealing only a portion of the data on which government experts based their analysis, released two weeks ago.

The testimony came as a new independent study, published in the journal Science, reported that a vast fog of oil — 22 miles long and more than a mile wide — is floating far below the Gulf’s surface, where low water temperatures are slowing its natural breakdown.

It was the most conclusive evidence yet of a subsea oil “plume” that could linger for years, said Richard Camilli of the Woods Hole Oceanographic Institution in Massachusetts, the lead author of the report.

While scientists don’t know the long-term impact of that much oil floating below the water’s surface, they urged the Obama administration not to make it seem that the worst of the spill is over.

“We understand that the government wants to turn a corner and wants to signal that the Gulf is on the road to recovery,” Lisa Suatoni, a senior scientist with the oceans program of the Natural Resources Defense Council, an environmental group, told a congressional panel Thursday.

“However, the facts simply do not bear that out. There is still a huge amount of oil in the environment.”

The government’s report, produced by senior officials from the National Oceanic and Atmospheric Administration and the U.S. Geological Survey, claimed that at least half of the oil that spilled from BP’s Deepwater Horizon rig was gone from the environment and much of the remainder is degrading rapidly underwater.

Several independent scientists have slammed the report, noting that it counted as part of the spill some 800,000 barrels that were siphoned immediately to surface ships, giving an incorrect impression of how much oil was discharged into the Gulf. Earlier this week, researchers from the University of Georgia reported that 70 to 79 percent of the spilled oil remained in the water, and that far less oil had evaporated than the government claimed.

Bill Lehr, a senior scientist with NOAA, acknowledged at Thursday’s hearing that only 10 percent of the spill had been skimmed or burned off by recovery efforts. Anywhere from 60 to 90 percent of the discharged oil remains in the Gulf in some form, much of it broken up by chemicals, he said.

When Lehr said it would take another two months to release the data and algorithms that were used in the report, Rep. Edward Markey, the Massachusetts Democrat who chaired the hearing, said that was unacceptable.

“”This report … is giving many people a false sense of confidence regarding the state of the Gulf,” Markey said.

“It is important for that information right now, Dr. Lehr, to be made public. If your numbers are wrong, two months from now could be too late.”

Lehr responded: “I will do whatever I can to speed up the report.”

Federal environmental officials told Markey — the chairman of the House Energy and Environment Subcommittee and the only member who was present for the rare recess hearing — that they hadn’t uncovered signs that the spill contaminated seafood.

Donald Kraemer, a senior food safety official with the Food and Drug Administration, said the agency had tested some 500 animals — including shrimp, crab and oysters — from Gulf waters and found oil contaminant levels to be roughly the same as they were before the spill.

Kraemer also said it was unlikely that the chemical dispersants that were used to clear up the spill would pose a danger to humans.

“The current science indicates a low risk that these dispersants will concentrate in seafood,” he said. He added that the FDA and NOAA were still testing seafood, though.

However, Suatoni of the Natural Resources Defense Council said the government had released data of fewer than 100 samples of fish and none of shrimp.

“The seafood monitoring done may not be adequate in terms of sample size,” she said.

Ian MacDonald, a Florida State University oceanographer, also cast doubt on the government’s claim that oil “is biodegrading quickly” in the ocean, arguing that scientists still don’t know how fast hydrocarbon-eating bacteria are working. MacDonald, who’s 58, said the spill would remain in the Gulf in some form for the rest of his life.

Shashank Bengali is the Los Angeles Times' South Asia correspondent, covering India, Pakistan, Afghanistan and surrounding countries. Previously he was a national security reporter based in Washington, DC. He came to The Times in 2012 from McClatchy Newspapers, where he served as bureau chief in Nairobi, Kenya; correspondent in Cairo and Baghdad; and national security editor in Washington. Over the past decade, he has reported from more than 40 countries and introduced readers to Somali pirates, Afghan warlords, Chinese race-car drivers, Nigerian film stars, Arab revolutionaries and other larger-than-life characters. He's also written from overseas for Playboy magazine. Originally from Cerritos, he studied journalism at USC and earned a master's in public policy from Harvard University.

W.J. Hennigan covers the Pentagon and national security issues from the Los Angeles Times' Washington, DC, bureau. Previously, he was the aerospace and defense beat writer based in Los Angeles for more than five years. Before joining the paper, Hennigan braved Arizona's desert heat, covering business for the East Valley Tribune. He also previously worked in the nation's capital, writing for the Legal Times. Hennigan grew up on the south side of Chicago and has degrees from Northern Illinois University and Arizona State University.

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